How decode is used in SQL with example?

In Oracle, DECODE function allows us to add procedural if-then-else logic to the query. DECODE compares the expression to each search value one by one. If expression is equal to a search, then the corresponding result is returned by the Oracle Database. If a match is not found, then default is returned.

What is SQL decoding?

Introduction to SQL DECODE() DECODE function in Standard Query Language (SQL) is used to add procedural IF – THEN – ELSE like statements to a query. It compares a given expression with each search value one by one and returns a result on the basis of outcomes received from the comparison.

What is the output of select decode null null 1 0 from dual?

Oracle DECODE Function with NULL Values It treats a NULL expression and NULL search as equal (so NULL == NULL). So, this example will return 1: SELECT DECODE(NULL, NULL, 1, 0) FROM DUAL; The CASE statement treats NULL values as not equal, so this is an important distinction when working with this function.

What is the difference between decode and case with examples?

DECODE performs an equality check only. CASE is capable of other logical comparisons such as < > etc. It takes some complex coding – forcing ranges of data into discrete form – to achieve the same effect with DECODE. An example of putting employees in grade brackets based on their salaries.

Can we use decode inside decode?

It is possible to use DECODE, but you’d have to use nested DECODEs and you’d end up with something that’s much harder to read, understand and therefore maintain.

How do I use decode?

The DECODE function returns a value that is the same datatype as the first result in the list. If the first result is NULL, then the return value is converted to VARCHAR2. If the first result has a datatype of CHAR, then the return value is converted to VARCHAR2. If no matches are found, the default value is returned.

Is decode faster than case Oracle?

From performance perspective, In Oracle decode and CASE does not make any difference. But in Exadata , Decode is faster than CASE. The Decode operation is done at storage Server level where the data is present BUT CASE is done at DB Instance level which receives data from DB storage Level.

What is decode write an example query?

Parameters or Arguments All search values are automatically converted to the data type of the first search value before comparing. The value returned, if expression is equal to search. Optional. If no matches are found, the DECODE function will return default.